A known packaging machine has an upwardly facing surface which can slidably support articles to be conveyed, and has a plurality of pushing assemblies at spaced locations along an endless chain, each pushing assembly moving horizontally above the surface along one reach of the chain and having a plurality of rigid, downwardly projecting fingers which can engage the article and slide it along the surface. The article is located between two guide members, and the distance between the guide members can be adjusted to accommodate articles of different sizes.
One such machine is used for bakery products such as hamburger buns and hot dog buns, and the distance between the guide members is adjusted to accommodate different types of buns, or variation of the number or configuration of buns in each group of buns being slid across the surface. In this known machine, the preferred distance between the outermost fingers of each pushing assembly is preferably only slightly less than the distance between the two guide members. Thus, when the distance between the guide members is increased or decreased, different pushing assemblies are used. In particular, every pushing assembly on the endless chain is manually removed from the chain and replaced with a similar pushing assembly of larger or smaller width. The known machine typically has ten to fifteen pushing assemblies on the chain. Thus, although the machine has been satisfactory for its intended purposes, it has some disadvantages.
In particular, the machine must be turned off for at least thirty minutes to an hour while all of the pushing units are changed, which obviously is downtime during which no products are being produced and which also necessitates the expense of the manual labor involved in effecting the replacement of the pushing assemblies. Moreover, several separate sets of pushing assemblies, each set including ten to fifteen pushing assemblies, must be purchased and maintained, which involves significant expense as well as the risk that a necessary set or at least one pushing assembly of a set may be lost or misplaced, thereby creating additional downtime and expense until the problem can be remedied. There is also the problem that, if the operator forgets to change to narrower pushing assemblies when the distance between the guide members is decreased, the outer fingers of the pushing assemblies may be jammed against the guide members during operation of the machine, thereby bending or breaking the pushing fingers and/or the guide members, which leads to the expenses associated with downtime as well as the actual costs of repairing or replacing the damaged pushing fingers and/or guide members. Moreover, there is the risk of physical injury to the person changing the pushing assemblies in the event the machine is inadvertently turned on during the replacement process.
It is therefore an object of the present invention to provide an apparatus of the type discussed above which avoids the need to change all of the pushing assemblies when adjusting the distance between the guide members, in particular by providing a single set of pushing members which each have an effective width which can be varied.
It is a further object of the invention to provide such an apparatus in which the adjustment of the effective width of the pushing assemblies is carried out automatically in response to movement of one or both guide members.
It is a further object of the invention to provide such an apparatus in which the automatic adjustment of the effective widths of the pushing assemblies can be carried out in a very short period of time, while the machine is running, and without any need for an operator to contact movable parts of the machine which might cause physical injury.
It is a further object of the invention to provide such an apparatus which is durable, rugged, and requires little or no maintenance.
It is a further object of the invention to provide such an apparatus which operates smoothly, efficiently and quietly.